We propose to investigate the role of specific DNA-protein complexes in the regulation of gene expression. The mechanism of transcription initiation by RNA polymerases will be studied. The role of mutation in altering this process will be investigated using lac operon DNA. Tumor virus SV40 DNA and chromatin will be transcribed in vitro by RNA polymerase II. Modulation of transcription by histones will be studied using reconstituted nucleosomes. Methodology utilized includes in vitro synthesis and sequence analysis of RNA, chemical and enzymatic probes of nucleoprotein complexes, and mutant recombination in vitro. It is hoped that study of these genes will enhance our understanding of normal and abnormal cellular regulation.